Patent GB-236673-A (GB)
Title: Improvements in or relating to systems for the transmission of electromagnetic radiant energy
IPC: H03B11/08
Filed: 1924-04-14
Abstract: 236,673. Jackson, W. J. Mellersh-, (Taylor, A.). April 14, 1924. Arc oscillation generators; keying systems; multiplex systems.-In high-frequency generators, particularly Poulsen arc oscillators, the operation of the system is stabilized by utilizing the principle that the generator has an inherent tendency to function in such a manner as to prevent waste of energy. An energy absorber, in which appreciable energy loss occurs only when the operation of the source becomes unstable, is coupled to the source and acts automatically to prevent any deviation from the desired conditions. In the arc system shown in Fig. 1, an inductance 25 and capacity 27 is tuned to the desired frequency of emission, giving a potential nodal point 31 with respect to ground, across which is inserted a resistance 29. Any variation in frequency of emission, or the production of harmonics, will increase the potential difference across the resistance 29 and lead to an increased energy dissipation, which will be abhorrent to the are, the resistance, thus acting as a stabilizer. It will also tend to bypass such extraneous currents to earth and present their radiation. For signalling the resistance 29 is short-circuited by the keys 37, a second absorption circuit 38, 39 being simultaneously closed by a key 40 in order to maintain a constant load on the are 11. The autotransformer coupling 15 between the oscillatory circuit and the aerial 13 allows the operation of the arc to be adjusted to the optimum efficiency point on its current-voltage characteristic. The coils 33, 34 are adjusted so as to counterbalance any coupling between the coils 25 and 15. By stabilizing the frequency in this way, interference between adjacent aerials is minimized, enabling several transmitters to operate in the same locality, even with appreciable capacitycoupling between the respective aerials. Fig. 2 illustrates a system employing the known device of paralleling the arc 42 with a second circuit comprising a coil 48 and condenser 10 in series with the aerial, for the purpose of stabilizing arc operation. In order to avoid loss of energy over the loop circuit so formed. a second coil 45 is so coupled to the coil 48 that for normal operation the magnetomotive forces cancel, whilst for undesired cross-currents they add, thus setting up an energy waste, which tends to restore the are to normal operation. Fig. 3 shows two arcs 50, 51 working in parallel, cross-currents being prevented by the provision of condensers 55, 56 so adjusted as to create equal potentials at the points 58, 59 for normal operation. Any departure will lead to energy waste across the bridging resistances 60, which therefore acts as a stabilizer. The production of harmonics is similarly resisted. Variations in frequency in the systems shown in Figs. 2 and 3 can also be prevented by utilizing the tuned system of Fig. 1 in combination with a bridging resistance to ground. Instead of using a pure resistance such as 29, Fig. 1, a rejector circuit may be used as an energy absorber. Fig. 6 shows the system of Fig. 2 applied to two thermionic oscillators 77, 78 feeding the aerial 79 in parallel through an iron-cored inductance 80 in which losses are set up by any variation from the desired operating conditions.